@ehehejhuhe I'm so sorry but this is the Opera GX Forum. The ultraviolet, hackerman, GX classic and other themes are only available for the Opera GX browser. I see that you're using the normal Opera browser.
You can download the Real Opera GX browser by going to https://www.opera.com/gx
TL;DR: You are using the normal Opera browser. You didn't install Opera GX. Download it at https://www.opera.com/gx